With the ever expanding frontiers of space and aviation, and with modern aircraft now operating at altitudes which only a few decades ago were thought to be impossible, it is becoming increasingly important to overcome some problems introduced by high altitude flight. At high altitudes, the ambient light is often quite bright and may adversely effect the performance of optical avionics equipment.
One particular type of avionics equipment in which high ambient light is posing vexing problems, is head-up displays. Basically, head-up displays utilize a reflecting combiner disposed on the aircraft wind screen so that an image generated by a video display device in the cockpit is projected upon the wind screen but still allowing the pilot to view the outside through the wind screen.
Three dimensional head-up displays have been attempted in the past, but often with undesirable aspects associated with them. For example, attempts have been made to mount the display generating devices on the pilots helmet. Such a device is shown in U.S. Pat. No. 4,315,241 entitled "Visual Display Apparatus issued on Feb. 9, 1982 to Archer M. Spooner which application is incorporated herein by this reference. Another attempt is described in U.S. Pat. No. 4,575,722 entitled "Magneto-Optic Display" issued on Mar. 11, 1986 to Robert H. Anderson, which is incorporated herein by this reference. The Anderson display utilizes a mechanically rotating mirror to reflect light into the pilot's eyes.
While these designs or variations of them, have been suggested in the past, they have several serious drawbacks. The Spooner invention requires the addition of light emitting devices to be mounted on the pilot's helmet. This increases the weight of the pilot's helmet and allows for only small and frequently low brightness video displays. The Anderson invention includes the mechanically rotating mirror which has the obvious disadvantage of moving parts.
Consequently, there exists a need to provide a 3D, non-helmet mounted head-up display which has high brightness and low helmet weight.